• Tuberculosis and Respiratory Diseases
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• v.41 no.4
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• pp.372-378
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• 1994

Background: Pressure support ventilation(PSV) is a new form of mechanical ventilatory support that assists spontaneous inspiraory effort of an intubated patient with a clinician-selected amount of positive airway pressure. Low level pressure support during inspiration can overcome the resistive component of inspiratory work imposed by an endotracheal tube. However the clinical efficacy of PSV as a weaning method has not been established yet. Object: The aim of study was to evaluate the efficacy of PSV when it is added to intermittent mandatory ventilation(IMV) in facilitating weaning precess compaired to IMV mode alone. Method: When the subject patients became clinically stable with their arterial blood gas analysis in acceptable range, they underwent weaning process either by IMV alone or by IMV plus PSV. The level of pressure support was held constant throught the weaning period. For the patients who required mechanical ventilation for less than 72 hr, 2h weaning trial was performed with IMV rate starting from 6/min. For the patients who required mechanical ventilation more than 72 hr, 7 hr weaning trial was performed with IMV rate starting from 8/min. For the patients who failed three consecutive trials of weaning, retrial of weaning was attempted over 3 days with IMV rate starting from 8/min. Clinical characteristics, APACHE II score and nutritional status were compared. For all patients, heart rate, mean blood pressure and respiratory rate were mornitored for 48 hrs after weaning trial started. Results: The total number of weaning trial was 37 in 23 patients(18 by IMV, 19 by IMV+PSV). Total ventilation time, APACHE II score and nutritional status were not statistically different between the two groups. The weaning success rate were not statistically different(38.3% by IMV, 42.1% by IMV+PSV) and the changes of mean blood pressure, heart rate, respiratory rate during first 48 hours were not different between the two groups. Conclusion: Low level PSV when added to IMV for weaning trial does not seem to improve the success rate of weaning from mechanical ventilation. PSV at 10cm $H_2O$ did not induce significant physiologic changes during weaning process.

• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.173-178
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• 1999

Purpose : To evaluate the usefulness of functional MRI (fMRI) of visual cortex in patients with ischemic infarction in the occipital lobe. Materials and Methods : Four patients with the symptoms and signs of visual cortical ischemia were included. Functional MRI was performed by 2D-FLASH technique with the parameter of 90/56msec TR/TE, $40^{\circ}$ flip angle, $240{\times}240{\;}FOV,{\;}64{\times}128$ matrix number, 8.32 seconds acquisition time, 8mm slice thickness. An axial slice including both visual cortices was selected and alternative activation and resting of the visual cortex was performed using red color photostimulator. all patients undertook visual field test, and vascular abnormality was examined by MRA (n=4) and DSA (n=2). fMRI results were compared with the results of a visual field test, conventional MRI and cerebral angiography. Results : On fMRI, decreased activity of the visual cortex was found in the occipital lobe corresponding to stenosis of the posterior cerebral artery or its branch noted on angiogram. However, 2 of 4 patients showed no abnormal findings on conventional MRI. Visual field defect was noted in 3 patients, one and of whom showed no abnormality on conventional MRI and diffusion-weighted image, but revealed decreased activity in the corresponding visual cortex on fMRI. Conclusion : fMRI may be a sensitive method for detection of the status of decreased blood flow or vascular reserve which other methods can not.

• The Korean Journal of Nuclear Medicine
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• v.34 no.1
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• pp.82-93
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• 2000

Purpose: We characterized the signals obtained from the components of a small gamma camera using Nal(Tl)-position sensitive photomultiplier tube (PSPMT) and optimized the parameters employed in the modules of the system. Materials and Methods: The small gamma camera system consists of a Nal(Tl) crystal ($60{\times}60{\times}6mm^3$) coupled with a Hamamatsu R3941 PSPMT, a resister chain circuit, preamplifiers, nuclear instrument modules (NIMs), an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a resistive charge division circuit which multiplexes the 34 cross wire anode channels into 4 signals (X+, X-, Y+, Y -). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated and digitized via triggering signal and used to localize the position of an event by applying the Anger logic. The gamma camera control and image display was performed by a program implemented using a graphic software. Results: The characteristics of signal and the parameters employed in each module of the system were presented. The intrinsic sensitivity of the system was approximately $8{\times}10^3$ counts/sec/${\mu}Ci$. The intrinsic energy resolution of the system was 18% FWHM at 140 keV. The spatial resolution obtained using a line-slit mask and $^{99m}Tc$ point source were, respectively, 2.2 and 2.3 mm FWHM in X and Y directions. Breast phantom containing $2{\sim}7mm$ diameter spheres was successfully imaged with a parallel hole collimator. The image displayed accurate size and activity distribution over the imaging field of view Conclusion: We proposed a simple method for development of a small gamma camera and presented the characteristics of the signals from the system and the optimized parameters used in the modules of the small gamma camera.

• Childhood Kidney Diseases
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• v.9 no.1
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• pp.38-45
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• 2005

Purpose : The purpose of this study was to analyze the therapeutic effect of plasmapheresis in various pediatric diseases. Methods : Therapeutic plasmapheresis was performed by COBE Spectra centrifugation. Nine cases were included in this study. The number an[;. method of plasmapheresis, together with the progress and prognosis of each case were retrospectively reviewed. Results : The patients' ages ranged from 26 mont]Is to 16 years of age, and the mean age was 9.9 years. There were S males and 4 females. The underlying diseases requiring plasmapheresis included 2 cases of hemolytic uremic svndrome(HUS), 1 case of lupus nephritis, 2 cases of rapidly Progressive glomerulonephritis(RPGN), 1 case of focal segmental glomorulosclerosis(FSGS), 1 case of systemic vasculitis after pulmonary hemorrhage, 1 case of acute renal failure associated with pulmonary hemoIThage, and 1 case of acute rejection after renal transplantation. The average number of plasmapheresis performed was 6.2 times with a range of 3 to 13 times. The patients with HUS, lupus nephritis, ANCA positive systemic vasculitis induced by pulmonary hemorrhage and ARF-associated pulmonary hemorrhage showed a good response to therapeutic plasmapheresis, but the patients with RPGN, refractory FSGS, and acute rejection after renal transplantation were not responsive to treatment. The most common side effect was hypocalcemia which was rarely symptomatic. Vital signs were not compromised. Conclusion : Although it is presumptuous to generalize the therapeutic effects of plasma pheresis in different diseases due to the small number of study subjects, this study shows that plasmapheresis may be an effective therapeutic modality in various pediatrics diseases and should be considered as a therapeutic option.

• Clean Technology
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• v.29 no.4
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• pp.255-261
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• 2023

Power semiconductors are semiconductors used for power conversion, transformation, distribution, and control. Recently, the global demand for high-voltage power semiconductors is increasing across various industrial fields, and optimization research on high-voltage IGBT components is urgently needed in these industries. For high-voltage IGBT development, setting the resistance value of the wafer and optimizing key unit processes are major variables in the electrical characteristics of the finished chip. Furthermore, the securing process and optimization of the technology to support high breakdown voltage is also important. Etching is a process of transferring the pattern of the mask circuit in the photolithography process to the wafer and removing unnecessary parts at the bottom of the photoresist film. Ion implantation is a process of injecting impurities along with thermal diffusion technology into the wafer substrate during the semiconductor manufacturing process. This process helps achieve a certain conductivity. In this study, dry etching and wet etching were controlled during field ring etching, which is an important process for forming a ring structure that supports the 3.3 kV breakdown voltage of IGBT, in order to analyze four conditions and form a stable body junction depth to secure the breakdown voltage. The field ring ion implantation process was optimized based on the TEG design by dividing it into four conditions. The wet etching 1-step method was advantageous in terms of process and work efficiency, and the ring pattern ion implantation conditions showed a doping concentration of 9.0E13 and an energy of 120 keV. The p-ion implantation conditions were optimized at a doping concentration of 6.5E13 and an energy of 80 keV, and the p+ ion implantation conditions were optimized at a doping concentration of 3.0E15 and an energy of 160 keV.

• Childhood Kidney Diseases
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• v.3 no.2
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• pp.130-144
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• 1999

Purpose : Long-term use of Cyclosporine(CsA) reduce renal blood flow by afferent arteriolar vasoconstriction and lead to chronic pathologic changes of CsA nephrotoxicity - 1) interstitial nephritis(IN); tubular atrophy (TA) and/or interstitial fibrosis(IF),2) arteriolopathy(AP). The Object of this study is to estimate the incidence of chronic pathologic CsA nephrotoxicity by duration of treatment and type of renal disease, relationship between histologic and clinical nephrotoxicity, and optimal duration of CsA therapy. Methods : 102 children with steroid resistant or dependent nephrotic syndrome confirmed by renal biopsy and treated with CsA from 1986 to 1997 were enrolled in this study(58 MCNS, 10 FSGS, 10 MGN, 15 $Henoch-Sch\"{o}nlein$ purpura nephritis with nephrotic syndrome (HSPN) and 9 IgA nephropathy with nephrotic syndrome(IgAN)). CsA was administered for 1yr, 1.5yr, 2yr in 24, 12, 22 MCNS patients and 2, 2, 6 FSGS patients respectively, 1yr, 2yr in MGN and 1yr in HSPN and IgAN. Sequential biopsies were done in all 102 patients after CsA treatment for evaluation of pathologic nephrotoxicity. Results : Complete remission rate was 92.2% (100% in MCNS and MGN, 80% in FSGS, 86.6% in HSPN and 55.5% in IgAN). Incidence of relapse during 6months after CsA treatment was significantly decreased compaed with relapsing spisodes during 6months before CsA treatment in MCNS(P<0.0001) and FSGS(P<0.0001). According to pathologic changes, 71 patients(69.6%) showed no pathological change, 24 patients(23.5%) showed IN and 7 patients(6.8%) showed AP. IN was 16.6%, 33.3%, 27.2% in 1, 1.5, 2 year of CsA treatment group in MCNS. AP was 0%, 16.6%, 9% in 1, 1.5, 2 year of CsA treatment group in MCNS. 14 out of 58 MCNS(24.1%) showed IN and 4 out of 58 MCNS(6.8%) showed AP. Incidence of pathologic change was significantly lower in CsA therapy of <1yr than >1yr(P=0.03). There were no significant difference of incidence of pathologic change in original renal disease, age and sex. Conclusion : Duration of CsA treatment was significant risk factor for nephrotoxicity and optimal duration seemed to be 1 year. Pathologic change due to nephrotoxicity did not correlate with deterioration of renal function and only detectable by renal biopsy.